1. Field of the Invention
The present invention relates to a storage bag for storing fermented foods such as coffee beans (including ground coffee beans) and soybean pastes (miso), ferment, bleaching agent and the like, such that gas generated by such contents can be discharged.
2. Related Art
As a storage bag for storing fermented foods such as coffee beans and soybean pastes, a storage bag provided with a gas vent for discharging gas is conventionally known.
When the contents are coffee beans, the storage bag may be provided with a gas vent for discharging gas which is smaller than coffee beans, but if the contents are soybean pastes, in order to prevent the soybean pastes from leaking, a position of the storage bag where the gas vent for discharging gas is provided is limited. Therefore, when the contents are soybean pastes, there is a problem that the gas vent for discharging gas must be provided in an upper end of the storage bag, and the storage bag must be in storage on display in a state in which the storage bag is in an upright position.
Hence, in order to solve such a problem, the present assignee proposes a storage bag as disclosed in Publication of Japanese Unexamined Patent Application No. 11-1243 for example.
According to the storage bag disclosed in this publication, the storage bag body stores contents which breathes and generates gas, and an air passage is formed in a portion of the storage bag body. A film layer made of synthetic resin is provided on a position of the storage bag body corresponding to this air passage. A large number of particles made of material which is not melted at a melting point of the film layer are allowed to exist on the film layer in its thickness direction. An outer diameter of the particle is smaller than a thickness of the film layer. The film layer is drawn.
The film layer used for the storage bag having the above-described structure is formed with a large number of fine gaps directing substantially in the drawing direction such as to surround the particles. In an arbitrary position of the film layer, the large number of gaps are connected to each other such as to pass through the film layer in its thickness direction. If the contents breathes and generates gas and a pressure in the storage bag reaches a given pressure, gas is pushed and discharged from the large number of gaps which are connected in the thickness direction of the film layer and which are located on the air passage. By repeating this phenomenon, the storage bag can maintain its state in which the storage bag is expanded to such a degree that the storage bag is not ruptured. The fine gaps formed in the film layer have such size that the contents do not leak therethrough, and even if the storage bag is in an upright position or a horizontal position, the contents do not leak and gas can be discharged.
In the case of the storage bag disclosed in this Publication of Japanese Unexamined Patent Application No. 11-1243, however, on the film layer provided at the position of the air passage, a large number of particles made of material which is not melted at a melting point of the film layer and each having an outer diameter smaller than the thickness of the film layer exist in the thickness direction of the film layer. Such a film layer which is different from the material of the storage bag body must be prepared and the film layer must be mounted on the position of the storage bag body corresponding to the air passage, and there is a problem that the cost of the storage bag body is increased.